Space vehicles, such as space shuttles, rockets, satellites, missiles, etc., may be exposed to hostile conditions characterized by high temperatures and turbulence during flight (e.g., launch, ascent, re-entry, etc.). Such space vehicles are formed of multiple components secured together or in adjacent relationship, and may require both thermal protection systems and electrical protection systems to protect the space vehicle from damage that may be caused during flight.
For example, a space vehicle may be exposed to extreme temperatures such as exhaust plumes, heat generated by atmospheric friction during launch and re-entry, etc. Excessive heat may damage one or more portions of the space vehicle, including, for example, wings, nozzles, a nose cone, fuel tanks, engine exhaust ducts, re-entry shield surfaces, etc. Accordingly, space vehicles are often equipped with a thermal protection system (TPS), which may be incorporated in one or more parts of the space vehicle that are exposed to high temperatures or large temperature gradients. A TPS conventionally employs assemblies in the form of a multi-component structure comprising a plurality of insulative panels or tiles attached to the surface of a structure or member that is intended to be protected by the TPS, such as on outer surfaces of a re-usable space shuttle used by NASA. Conventional composite materials may include reinforced carbon-carbon (RCC), fibrous refractory composite insulation tiles (FRCI), ceramic matrix composites (CMCs), etc. Such thermally insulative materials are designed and configured to protect the space vehicle frame from temperatures encountered during flight, such as re-entry into Earth's atmosphere (which temperatures may exceed about 1,260° C.).
In addition to thermal protection systems, space vehicles conventionally include one or more systems to protect the space vehicle from direct and indirect lightning strikes (lightning strike protection (LSP) systems), electrostatic discharge (ESD), or electromagnetic interference (EMI). For example, a lightning strike protection system may provide a relatively low electrical resistance pathway from a location of a lightning strike to a location where electric charge from the lightning strike can dissipate, to reduce or prevent damage to the spacecraft. In addition, charges may build up on surfaces of the space vehicle over time (such as by triboelectrification), eventually resulting in ESD. The ability to effectively manage lightning strikes and ESD on composite materials that form structural components of space vehicles is a significant safety consideration for the space vehicles.
Conventional thermal protection systems, which include materials that are disposed on exterior surfaces of the space vehicle, often include electrically insulative composite materials. Thus, in some instances, the space vehicle may include an electrically conductive film on exterior surfaces of the space vehicle, or multi-layered composites that include conductive meshes or foil layers to dissipate charge from lightning strikes or ESD. However, some foils may be expensive and prone to mechanical failure. Further, high currents from lightning strikes or ESD may damage sites of electrical discontinuity where the current may arc, such as at locations between composite panels, mechanical fasteners, joints, fiber interfaces, etc. Electrically conductive adhesives disposed between adjacent panels may include a large volume of silver filler materials to provide electrical conductivity to the conductive adhesive. However, the large volume of silver required for sufficient electrical conductivity reduces an adhesion strength of the adhesive and, thus, materials adjoined by the adhesive may debond in the event of a lightning strike or ESD. Further, the large volume of silver may also be cost prohibitive in many applications.